How to use windows 8 on a brand new system

Buy Windows 8, and install it.

how much is it? cant i use the beta

The Beta is not a finished product, and if you run into any problems, the first thing anyone will say is to get the final product. You could go with something like Linux.

http://www.tomshardware.com/news/Windows-8-Price-Promot...

You may be able to get an OEM copy for less, but it will will be tied to pc once installed(and activated).
http://www.tomshardware.com/news/microsoft-windows-8-li...

You can use the beta, but it will expire.

Windows 7 has a 30 day trial period. Gives you a little time to save up to buy the license.

You can't buy windows 8 because it's not out yet. You can install the beta like any other windows, either put it on a bootable external device (ei flash drive) or a cd. When it is released, it will ask to upgrade/buy the release version, the same way windows 7 beta was handled.

so if i download the beta when windows 8 actually comes out will i get it for free? can i download windows 8 beta and put it on a disk on a mac

You can't get Winsows 8 for free. You have to but it. You can use the Beta, but just understand that it is not a complete OS(it's a testing version), and you may find an issue that won't be supported.

the only legitimate way of getting windows for "Free" is if you are in a college/university with a Dreamspark/MSDNAA program as a computer science student. other than that, there isn't a free version of windows, and you would have to use something like Linux until you can pay for a windows license.

Once you have installed Windows 8 (you can install Windows 8 Enterprise final for free for 90 days now ) to make it useable you must install ClassicShell or similar program to get the start menu back so that you can forget Metro.